Abrasion resistant finishes containing polyethylene



Patented Aug. 15, 1950 T ABRASION RESISTANT FINISHES CONTAININGPOLYETHYLENE Daniel M. Gowing,

Swarthmore,

Dorothy R.

Langdon, Philadelphia, and Royce L. Selby, Lansdowne, Pa., assignors toE. I. du Pont de Nemoursdz Company, Wilmington, 'Del., a corporation ofDelaware I No Drawing.

This invention relates to protective coatings, and particularly tocoating compositions which possess a high degree of abrasion resistance.

With the development of new and improved synthetic resin materials;their .use in coating compositions has been greatly extended. Markedprogress has been made in the development of both air dry andbakingsynthetic resins, enamels and clears. Although such protective coatingshave yielded, in general, satisfactory service, there are certainproperties in which improvement 'is desirable. Extensive commercial usehas been made'of white synthetic resin enamels for finishing sucharticles as refrigerators, kitchen cabinets and other kitchen;furniture, hospital equipment, dental furniture, and similar finishesare currently being used on automobiles, on furniture, both forhousehold and ofllce use, and on a large variety of industrialequipment. Compositions containing synthetic resins are likewise used onwood and composition floors and as a topcoating for linoleum and likefloor coverings. I

These finishes yield long and satisfactory service, but for some usesthey have been found deficient in resistance to abrasion. As examples offinished articles which are subject to large amounts of abrasion may bementioned the shelves of refrigerators where heavy dishes and milkbottles are caused to slide back and forth many times daily; floors inhomes, on steps and in public places; 'linoeum and other floorcoverings, in kitchens, bathrooms, etc., and automobiles, especially inregions where dust storms are prevalent, or whose owners frequentlypolish them with abrasive materials.

Many attempts for improving the mar-resistance of synthetic enamels havebeen made. One of these contemplates the addi ion of a small amount of awax such as candelilla, carnauba, beeswax or similar high me ting wax.While the prior art attempts have met with some success,most of themoffer diificulties in incorporating the modifying agent into the vehicleand nearly every such attempt decreases the overall ei'liciency of theunmodified coating composition. It ,is therefore apparent that thedevelopment of any successful means which increases the re- 'distance toabrasion of protective coatings for "the uses mentioned above, wouldbehighly desirable and of considerable commercial importance.

This invention has as its principal object the provision of protectivecoatings, the dry films Application September 10, 1946, Serial No.696,040-

! Olaims. (Cl. 260-114) of which will have a high degree of resistanc7to abrasion.

A further object is the provision of such protective coatings, having ahigh degree of resistance to abrasion interfering as little as possiblewith any of the other desirable properties of such coatings; as, forexample, gloss, color, hardness, flexibility, general durability andsatisfactory inter-coat adhesion.

Another object is to provide protective coatings by methods which aresimple and economical.

A still further object is the provision of means for incorporating anethylene polymer in a protective coating in such a manner that theabrasion resistance of the coating is enhanced.

Still another object is the provision of articles bearing a finishedcoating with improved resistance to abrasion.

Other objects will become apparent as the de- U. S. Patent 2,388,160.

Similarly, modified polymers of ethyleneaare advantageous according tothis invention, and particularly effective and valuable products for thepurposes outlined have been obtained when the polymerization of ethy eneis carried out in the presence of chain terminating agents, such asdioxolane, cyclohexane, methyl propionate, propionic acid anhydride,diethyl ether, methanol and hydrogen. The production of suchmodifiedethylene polymers is described in Peterson, et al., U. S.2,395,292, and in S. N. 438,466 (Hanford, et a1.) filed April 10, 1942,S. N. 445,012 (Loder, et al.) filed May 29, 1942, 532,219 (Roland, eta1.) filed April 21, 1944, 557,723 (Cooper) filed October 7, 1944, and583,394 (Roland et a1.) filed March 17, 1945, assigned to the assigneeof the present invention.

In theclaims and specification the term solid polymer of ethylene isintended to cover such polymers.

The invention will be more fully understood from the following examples,which are given by way of illustration and not of limitation, and inwhich the parts are by weight:

EXAMPLE I White baking refrigerator enamels A B C D Titanium Dioxide-24. 34 24. 34 24. 34 24. 34 Alkyd Resin 19.34 19.34 19.34 19.34Urea-formaldehyde Resin 19.34 19. 34 19. 34 19.34 5. 6 15. 67 15. 67 15.67 21. 24 20. 97 19. 89 07 07 07 Polymer of Ethylene 27 I l. 35

Abrasion Resistance:

Strokes to Failure 100 100 2, 200 30, 000-50, 000

1 The alkyd resin was a 43% dehydrated castor oil modified glycerylphthalate having an acid number oi approximately 12.

I This resin is a butanol modified urea-formaldehyde resin.

I This is a ratio oi about .7 of ethylene polymer to 100 oi binder.

I This is a ratio oi about 3.5 oi ethylene polymer to 100 oi hinder.

7 EXAMPLE 11 Air dry automobile enamel Ferrite Yellow 52 Alkyd Resin A.63 Alkyd Resin B .92 Lead Drier SolutiorL 86 Manganese Solutiom- 49Cobalt Drier Solution 76 Petroleum Nafihtha 62. 60 Polymer oi Et yiena1.23

Strokes to iailurc. 360 35, 000

Allwd resin A was a 52% linseed oil modified glyceryl phthalate havingan acid number of approximately 6.5.

Alkyd resin B was a 48% treated linseed oil modified glyceryl phthalatewith an acid number of 12.

The ratio of ethylene polymer to binder is about 2.7 to 100 in thisexample.

EXAMPLE III Orthodox floor varnish Varnish 1 40. 00 40. 00 Mineral Sp60.00 55. 24 Polymer oi Ethyl n I 4. 76

Strokes to iailurc 150 32, 000

l 45 gal. rosin ester varnish having a ratio oi oiticica/linseed- .4/l IThis is a ratio oi about 12 parts of ethylene polymer to 100 oi Themachine for testing the abrasion resistance was essentially a motordriven rubbing tool with an automatic counter. The rubbing tool was aone inch cylinder of glass with edges about 2 millimeters thick. Therubbing surface was of the ground glass" type and was so rounded thatonly about one square millimeter of actual rubbing surface was incontact with the surface to be abraded. There was a weight of 1 kilogramsuperimposed on the rubbing tool. The coatings tested were approximatelyti of an inch thick on metal. Failure was recorded when that thicknessof coating was abraded through. The term "abrasion resistance is used inthe claims to denote resistance of the film to relatively mild abrasionthroughout the entire thickness of the film, as distinguished from marresistance which indicates the resistance of the film surface only tosimilar abrasion.

The four examples show ratios of ethylene polymer to binder ranging from0.7 of polymer to of binder to 12 of polymer to 100 of binder. We

have found that less than the 0.7 part has butlittle eifect on theresistance to abrasion, and that when more than 15 parts areincorporated, the integrity of the film suffers. It becomes soft andcheesy and otherwise undesirable.

For most uses, we have found that ratios of about 4 of polymer to 100 ofbinder are to be preferred.

In order to obtain the full benefits from polyethylene polymers withrespect to abrasion resistance, it is desirable to have the polyethyleneuniformly dispersed throughout the film. Any method which accomplishesthis, such as dissolving it in the liquid vehicle, melting and mixinginto the liquid vehicle, etc., will give abrasion resistant properties.

Our preferred method for adding polyethylene polymer entails finelydispersing it in an excess of a non-solvent such as butyl alcohol byball milling or other suitable means. This yields a smooth milkypolyethylene dispersion which is then added directly to the coatingcomposition by agitation. This method is preferred because it givesproperties desirable in coating compositions other than abrasionresistance such as freedom from seed formation, maximum gloss, etc.

The preferred method of manufacture may be divided into two proceduresdepending upon the physical state of the ethylene polymer being used.

(1) If a coarse grade of ethylene polymer (e. g., sheet, granules,rollstoek, flake, etc.) is used it is heated with agitation with anequal weight of aromatic hydrocarbon such as toluene, xylene, etc.,until solution is complete. The solution may then be chilled quickly bymeans of a drum flaker to yield flakes of ethylene polymer/hydrocarbongel or it may be allowed to cool slowly with or without agitation toform a solid mass which is readily crushable. This ethylenepolymer/hydrocarbon gel-like mass is broken up into small pieces andcharged directly into a ball mill or other suitable grinding equipmentwith 1-2 times its own weight of normal butanol and ground for 10 to 15hours. The resulting dispersion of polymer is then added directly to thecoating composition in sufiicient quantities to give the range of .7 to15 parts of polymer for 100 parts of binder as shown in the foregoing.

(2) If the ethylene polymer is in a finely divided state known as "fiufiit may be charged directly into a ball mill or other suitable grindingequipment with l-2 times its own weight of normal butanol and ground for10-15 hours. The

resulting dispersion is then handled as described in the above method.

The ethylene polymers which we have found useful in promoting theabrasion resistance of protective coatings are all of those described inU. 8. Patent 2,153,553, Fawcett et al.';-2,388,160

' Krase; 2,395,292 Peterson et al., and those de- I scribedin S. N.438,466 Hanford et al. filed April 10,1042, now U. s. Patent No;2,440,800; s. N- 445,012 (Loder et al.) filed May 29,1942, now U. 8.Patent No. 2,394,862; S. N.'532,219 Roland et al.

' filed April 21, 1944, now U. 8. Patent No. 2,479,-

082; S. N. 557,723, Cooperfiled October 7, 1944 1 now U. S. Patent No.2,456,387 and S. N. 583,394,

' amounts, the increase being in some cases as much as'five hundredfold. Another advantage is that protective coatings which contain theethylene I polymers are much more resistant to becoming soiled or dirtythan are those without this addition.

It is apparent that many widely different embodiments of this inventionmay be made without departing from the spirit and scope thereof, and Itherefore, it is not intended to be limited except as indicated in theappended claims.

We claim: I

1. A non-aqueous coating composition which yields a tough, durable filmon drying which comprises organic fllm-forming material selected fromthe group cbnsisting of vegetable drying oil modified alkyd resins,monohydric alcohol modified urea-formaldehyde resins, andnitrocellulose; and from 0.7 to 15% by'weight thereof of a polymerofethylene which is solid at room temperature and has a compositioncorresponding to (CH2): and shows a crystalline structure by x-raydiffraction.

2. A rigid article having an adherent coating I of the composition ofclaim 1 on its surface.

'3, The composition of claim 1 in which the film-forming material is avegetable drying oil modified alkyd resin.

4. The composition of claim 1 in which the film-forming material isbutyl alcohol modified 6. In .the process of increasing the abrasionresistance of coating compositions which dry to a hard durable finish,the improvement which comprises preparing a smooth dispersion in anorganic liquid of a polymer of ethylene which is solid at roomtemperature and has a composition corresponding to (CH2): and showsacrystalline structure by X-ray diffraction; mixing with the saiddispersion an organic film-forming agent, the said dispersion beingpresent in an amount to yield a finished composition containing'from 0.7to 15 parts of the polymer of ethylene for each parts of film-formingagent in the composition, the said film-forming agent being selectedfrom the group consisting of vegetable drying oil modified alkyd resins,monohydric alcohol modified urea-formaldehyde resins, andnitrocellulose. I

7. The process of preparing abrasion-resistant finishes which comprisesgrinding a polymer of ethylene which is solid at room temperature andhas a composition corresponding to (cHm, and shows a crystallinestructure by X-ray diffraction, with from 1 to 2 times its weight ofhutanol for 10 to 15 hours and thereafter mixing therewith an organicfilm-forming agent and pigment, the said polymer of ethylene beingpresent in the finish in the amount offrom 0.7 to 15% by weight of thesaid film-forming agent, the said film-forming agent being selected,from the group consisting of vegetable drying oil modified alkyd resins,monohydric alcohol modified urea-formaldehyde resins, andnitrocellulose.

DANIEL M. GOWING. DOROTHY R. LANGDON. ROYCE L. SELBY.

I I REFERENCES CITED The following references are of record in the fileof. this patent:

UNITED STATES PATENTS Number Name Date 2,299,807 Dunbar Oct. 27, 19422,369,471 Latham Feb. 13,1945 2,395,292 Peterson et a1 Feb. 19, 19462,448,666 Fletcher et al Sept. 17, 1948 FOREIGN PATENTS Number CountryDate 507,323 Great Britain June 9, 1939 I Great Britain Nov. 15, 1939Certificate of Correction 2 Patent No. 2,518,462 August 15, 1950 DANIELM. GOWIN G ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows:

Column 3, line 58, for .4/1 read 4/1.;

and that the said Letters Patent should be read as corrected above, sothat the same may conform to the record of the case in the PatentOffice.

Signed and sealed this 21st day of November, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oommissz'oner of Patents.

1. A NON-AQUEOUS COATING COMPOSITION WHICH YIELDS A TOUGH, DURABLE FILMON DRYING WHICH COMPRISES ORGANIC FILM-FORMING MATERIAL SELECTED FROMTHE GROUP CONSISTING OF VEGETABLE DRYING OIL MODIFIED ALKYD RESINS,MONOHYDRIC ALCOHOL MODIFIED UREA-FORMALDEHYDE RESINS, ANDNITROCELLULOSE; AND FROM 0.7 TO 15% BY WEIGHT THEREOF OF A POLYMER OFETHYLENE WHICH IS SOLID AT ROOM TEMPERATURE AND HAS A COMPOSITIONCORRESPONDING TO (CH2)X AND SHOWS A CRYSTALLINE STRUCTURE BY X-RAYDIFFRACTION.